Magnetic targeting system and method of using the same

ABSTRACT

The present invention describes a magnetic targeting system suitable for guiding a biocompatible device to a target area within the body (in vivo) and method of using the same. The system includes a targeting member having a steering material and is attached to the biocompatible device. The system also includes at least one anchoring member constructed and arranged for the inclusion of a magnetic material effective for influencing the traversal of the steering material, in vivo. The magnetically influenced anchoring member interacts with the targeting member such that the biocompatible device is positionable relative to the target area.

This application is a reissue of U.S. Pat. No. 8,092,458 issued on Jan.10, 2012 and also claims benefit under 35 U.S.C. 120 as a continuationof U.S. patent application Ser. No. 14/152,985 filed on Jan. 10, 2014(now issued as U.S. Pat. No. Re. 45,436) which is also a reissue of U.S.Pat. No. 8,092,458 issued on Jan. 10, 2012. The entire disclosures ofthe above applications are incorporated herein by reference as if setforth in their entireties herein.

FIELD OF THE INVENTION

The invention generally relates to surgical implants; particularly to asystem and method for stabilization of adjacent bony structures; mostparticularly to a system to help navigate an interconnecting meansbetween multiple bony stabilization devices.

BACKGROUND OF THE INVENTION

It is widely held that healing and/or structural correction is greatlyfacilitated when a bone is stabilized in the proper position. Variousdevices for stabilization of bone are well known and routinely practicedin the medical arts. For example, an abnormal spine can be stabilizedusing a substantially rigid or semi-rigid interconnecting means (rod orplate) and fastening means (screws, clamps, hooks, claws, anchors, orbolts). Multiple fasteners are placed into the spinal pedicle of eachvertebra and linked by at least one interconnecting means. One of themore difficult aspects is the surgical insertion of the interconnectingmeans along a fixed path of delivery longitudinally along the vertebraeand through each of the multiple fastening means between multiplevertebrae. Once in place, this system substantially immobilizes thespine and promotes bony fusion (arthrodesis).

Traditionally, the surgical techniques for stabilization of bonerequired large incisions (upwards of 6 cm in length) and a considerableamount of muscle be cut and stripped away (retracted) from the bone foran “open” visualization of the bone and access thereto for the placementof the fasteners and instrument implantation. Although this so-called“open” surgical technique has successfully treated non-unions,instability, injuries and disease of the spine, it is not withoutdisadvantages. Given the invasive nature of this technique, a lengthyhealing time and considerable post-operative pain for the patient iscommon.

In response to aforementioned drawbacks, the surgical arts havedeveloped minimally invasive systems and procedures intended to replacethe more traditional open surgeries. Obviously, a less extensive systemand procedure will eliminate the need to perform much of the cutting andstripping of muscle, resulting in reduced recovery time and lesspost-operative pain. As a result, percutaneous procedures have beendeveloped which insert instruments and perform operations through smallskin incisions, usually between 1.5 and 5 cm in length, thereby reducingsoft tissue damage. However, smaller skin incisions and smaller surgicalfields require more novel and innovative approaches to perform thesecomplicated surgeries.

One such example of a minimally invasive system is the SEXTANT Spinalsystem by Medtronic (Memphis, Tenn.). This device is comprised of twobasic components, screw extenders, and the rod inserter, which resultsin an instrument that looks like a sextant used in naval navigation. Thedevice is an insertion tool that allows fasteners and interconnectingmeans to be applied to the spine in a minimally invasive manner. Thescrew extenders are long shafts used to deliver and attach screws to thevertebrae through small skin incisions. During surgery, these extendersprotrude outside the body, allowing the surgeon to arrange and jointheir ends so that the rod inserter may be attached. The rod inserter isan arc-shaped arm that swings along a fixed axis and pushes aninterconnecting rod though the skin and muscle and into the heads of theimplanted fasteners (pedicle screws).

While the aforementioned technique is adequate when the fastening meansare well aligned, it fails to deliver the rod when one of the screws ismisaligned. Moreover, the interconnecting rod must be pushed by thesurgeon along a fixed arch and cannot be directed around neuralstructures or bony obstructions. One consequence of forcibly pushing therod through the fastening means is the possibility of colliding the rodwith a bony obstruction causing a piece of bone to break off resultingin possible neurological damage. Another common problem is theinterconnecting rod becoming disengaged from the rod inserter. Wheneither of these incidents happen, additional surgery is often requiredto remove the bone fragment and rod from the wound. This may result inthe surgeon abandoning the minimally invasive approach and reverting toa traditional approach. Current spinal implant systems do not allow thecontour of the rod to match the normal curvature of the surroundinganatomy and such systems are not customizable to meet the individualanatomical variables that each patient presents.

In order to help avoid damaging sensitive anatomy and expedite implantassembly, various image-based navigation systems have been employedwhich utilize patient images obtained prior to or during the medicalprocedure to guide a surgeon during the surgery. Recent advances inimaging technology have produced detailed two and three dimensionalimages using optically guided, fluoroscopic guided, and electromagneticfield based systems. These image-based systems have also been used incombination with the previously described “open” surgeries. Onesignificant problem with most image-based systems is that the radiationgenerated is transmitted to the patient and surgical staff, which mayresult in physiological damage over time. Also, the cost and portabilityof this equipment continue to be an issue. In addition, these systemsoften require the surgeon undergo extensive training to operatecorrectly.

Accordingly, a need exists in the surgical arts for a system andminimally invasive procedure capable of providing optimal mechanicalsupport and bony fusion, while reducing the likelihood of bone damageand neural functioning when compared to the currently availableinterconnecting elements. It is also desirable to provide a surgicalprocedure that can be performed in conjunction with, but does notrequire, an image-based tracking system.

PRIOR ART

Although there are numerous patents directed to systems and methods forinsertion of a stabilizing implant at a selected area of an anatomy, theprior art nevertheless fails to teach a targeting system for theinsertion of an implant using minimally invasive techniques having adecreased risk of causing damage to neural structures or bonyobstructions using minimal, if any, radiation exposure to the patientand/or surgeon.

For example, U.S. Publication No. 2005/0085714 to Foley et al.,discloses a method and apparatus for percutaneous and/or minimallyinvasive implantation of a construct (e.g., spinal implant). Theconstruct may be implanted using a navigation system for planning andexecution of a procedure. A plurality of portions of the construct maybe interconnected using locations and paths determined and navigatedwith the navigation system. The navigation system utilizes optical orelectromagnetic localization to determine the precise location of aselected implant construct or instrument. An optical localizer can bepositioned relative to an extender attached to a screw. Alternatively, acoil may be positioned in an electromagnetic (EM) field such that theposition of the coil may be determined by sensing the induced voltage. Acomputer is used to form a plan prior to implantation of the constructand thereafter track the various portions of the construct duringinsertion. The plan and the tracking of the surgery are displayed on amonitor to provide guidance to the surgeon.

U.S. Publication No. 2005/0277934 to Vardiman, discloses a minimallyinvasive spinal fixation system used for spinal arthrodesis (bonyfusion) or motion preservation. The system comprises a plurality ofpedicle screws, including a first screw placed into a first vertebralbody, and a second screw placed into a second vertebral body, aconnector for attaching to the first and second screws and, a removableguide for percutaneously attaching the connector to the first and secondscrews. According to one embodiment, detectional spheres are positionedon the head of screw extenders and on the handle of the rod insertiontool. A comparator calculates the relative position of the insertiontool handle with respect to the screw extenders and provides a visualdisplay for the surgeon.

U.S. Pat. No. 6,236,875 to Bucholz, discloses surgical navigationsystems including reference and localization frames. The systemgenerates an image representing the position of one or more bodyelements during the procedure using magnetic resonance imaging(hereinafter, MRI) or computed tomography (hereinafter, CT) scan imagestaken prior to the surgery. The body elements and their relativeposition are identified during the procedure. The position of the knownbody elements can then be manipulated using a computer to the relativeposition of the patient during the surgery. The manipulated data canthen be utilized to guide the surgeon for implantation.

U.S. Pat. No. 6,226,548 to Foley et al., discloses an apparatus andprocedures for percutaneous placement of surgical implants andinstruments such as, for example, screws, rods, wires and plates intovarious body parts using image guided surgery. The invention includes anapparatus for use with a surgical navigation system, an attaching devicerigidly connected to a body part, such as the spinous process of avertebra, with an identification superstructure rigidly but removablyconnected to the attaching device. This identification superstructure,for example, is a reference arc and fiducial array which accomplishesthe function of identifying the location of the superstructure, and,therefore, the body part to which it is fixed, during imaging by CT scanor MRI, and later during medical procedures. The system utilizesemitters such as light emitting diodes (hereinafter, LEDs), passivereflective spheres, acoustics, magnetics, electromagnetics, radiologic,or micro-pulsed radars for indicating the location of a body part towhich the emitter is attached.

U.S. Pat. No. 7,011,660 to Sherman et al., discloses a braceinstallation instrument and method for the stabilization of bonystructures. The installation instrument is sextant-type tool with anchorextensions coupled to the anchors. The instrument is movable withrespect to the anchors to position a brace in a position proximate tothe anchors. The brace can be indexed for insertion at a predeterminedorientation with respect to the installation instrument.

All of the aforementioned prior art disclose a system which utilize animplant insertion means to forcibly push the surgical implant orinstruments to the target area in vivo. This increases the possibilityof pathway divergence and/or damage to neural and vascular structures.What has been heretofore lacking in the prior art is a simple andeconomical system and procedure for the accurate and precise placementof surgical implants and/or instruments at a target area while providinga decreased risk to neural and vascular structures. Moreover, none ofthe aforementioned references provide audible and/or tactile feedback tothe surgeon that indicate the target area has been reached.

SUMMARY OF THE INVENTION

The instant invention is related to a magnetic targeting system suitablefor guiding a biocompatible device, (implant, surgical instrument) to atarget area within the body (in vivo), be it a tumor or implantationpoint for a fastening means. The system includes a targeting member thatincludes a steering material. The targeting member is attached at oneend to the biocompatible device. The system also includes at least oneanchoring member constructed and arranged to secure to a target area invivo at one end and the other end constructed and arranged for inclusionof a magnetic material effective for influencing the traversal of thesteering material in vivo. The magnetically influenced anchoring memberinteracts with the steering material of the targeting member such thatthe connected biocompatible device is positionable relative to thetarget area.

It therefore an objective of the instant invention to provide a systemthat minimizes soft tissue damage and provides less post-operative pain.

It is a further objective of the instant invention to provide atargeting system that provides real time targeting by providing feedbackas to the position of the biocompatible device.

Yet another objective of the present invention is to disclose a feedbacksystem that utilizes audio and/or tactile feedback to indicate to thesurgeon when the target area is reached.

Another objective of the present invention is to provide a magnetictargeting system that can penetrate tissue without being distorted orcausing physiologic damage, unlike x-rays.

Still a further objective of the invention is to teach a targetingsystem which allows for shorter surgery, decreased x-ray exposure, andfewer complications for the patient.

Yet another objective of the instant invention is to provide a targetingsystem that is simple to operate to reduce the training the surgeon mustundergo for operation of peripheral systems.

These and other objectives and advantages of this invention will becomeapparent from the following description taken in conjunction with anyaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. Any drawings containedherein constitute a part of this specification and include exemplaryembodiments of the present invention and illustrate various objects andfeatures thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a partial side view of a portion of a patient's spinewhich includes magnetic targeting system according to a preferredembodiment of the invention;

FIG. 2 is the magnetic targeting system as shown in FIG. 1, illustratingthe targeting member with attached tethering means threaded through ananchor member;

FIG. 3 is the magnetic targeting system shown in FIG. 1, illustratingthe targeting member being removed from the interior of the patientthrough the last extender;

FIG. 4 is the magnetic targeting system as shown in FIG. 1, illustratingthe insertion of the biocompatible device between adjacent vertebrae;

FIG. 5 is a partial cross-sectional view of a portion of the extenderremovably attached to the connector portion of the multi-axial screw inaccordance with one embodiment;

FIG. 6 is an upper perspective view of a multi-axial screw that can beused in system of the present invention;

FIGS. 7a thru 7e illustrate various embodiments of the targeting memberused in the instant invention;

FIG. 8 is a partial side view of portion of the spine of a patient whichincludes the magnetic targeting system according to another embodimentillustrating the insertion of the targeting member in vivo without theuse of extenders; and

FIG. 9 illustrates a partial side view of a portion of a patient's spinewhich includes magnetic targeting system according to another embodimentof the invention using a permanent magnet.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the instant invention are disclosed herein,however, it is to be understood that the disclosed embodiments aremerely exemplary of the invention, which may be embodied in variousforms. Therefore, specific functional and structural details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representation basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

Referring now to FIGS. 1-9 which illustrate the magnetic targetingsystem 10 of the present invention suitable for facilitating navigationto a target area, wherein like elements are numbered consistentlythroughout. FIG. 1 shows a plurality of anchoring members 14 (alsoreferred to as fastening means). The anchoring members are depicted hereas multi-axial pedicle screws, each removably attached to an extender12a, 12b, 12c. Each of the extenders 12a, 12b and 12c has an open topand an aperture 30 adjacent a bottom end of each extender, asillustrated in FIGS. 1 and 2. These screws have a proximal end 16 and adistal end 18. The proximal end includes head portion 24 with a toolopening 26 configured to receive a driving tool (not shown). The distalend includes a threaded shank designed to secure to a selected targetarea located inside the body of a patient (in vivo), shown here asconsecutive spinal vertebrae V1, V2, V3. Although the target area isexemplified here as vertebrae in a partial spinal column, the targetarea may be located anywhere in vivo.

The screw shown here is a multi-axial screw where the proximal end ofthe screw may include a connector 28 rotatably connected to the headportion 24 of the screw. That is, the connector is capable of 360 degreerotation relative to the threaded shank 27 of the screw along the axis Lof the shank and angular motion defined by the angle α (FIG. 5). Oneexample of a suitable multi-axial screw is described in U.S. Pat. No.5,797,911, herein incorporated by reference. Although a multi-axis isexemplified herein, it is contemplated that a fixed axis screw may beused. Fixed-axis screws do not include a rotatable connector 28. Othermeans for anchoring are also contemplated herein, some of which include,clamps, hooks, claws, bolts, or the like. Moreover, the shank of theanchor member may or may be not be cannulated, as is known in the art.

As shown in FIGS. 5 and 6, the connector portion of the screw isconstructed and arranged to form a passageway 30 designed to removablyreceive implants of various sizes. The connector portion includes anopening 43 constructed and arranged to receive a set screw 38. As shownin FIG. 6, the head portion includes threaded interior sidewalls 46designed to mate with external threads 38 formed on the set screw. Thus,as the set screw is threadably lowered along the connector portion ofthe screw the passageway 30 in the connector is narrowed. The passagewayis narrowed until the exterior surfaces of the biocompatible device 44(shown here as interconnecting rod, see FIGS. 1-4) are sandwichedbetween the upper portion of the screw head 24 and the set screw. Thisacts to reliably secure the biocompatible device onto the screw. As withthe head of the screw, there should be a tool opening 40 configured toreceive a driving tool (not shown) inserted within the interior portion74 of the extenders. The driving tool is well known in the surgical artsand is used to rotatably secure the set screw to the desired positionwithin the interior of the connector.

As discussed above, the distal end 34 of each of the hollow extenders12a, 12b, 12c are removably attached to the screws by any appropriatemeans known in the art. For example, the extender may include adepressible member (not shown) located at the proximal end 33 of theextender that is operatively connected to an internal clamping memberlocated that the distal thereof. The clamping member is capable ofengaging and disengaging the connector portion of the screw. One exampleof a suitable extender which could be used in the present invention isdisclosed in U.S. Pat. No. 7,011,660, herein incorporated by reference.The extender may also be able to rotate the connector of a multi-axialscrew relative to the shank to facilitate the threading of theinterconnecting rod therethrough.

The extenders should be made of a substantially rigid biocompatiblematerial and have a length dimension (along its longitudinal axis 50)that allows the proximal end 33 to protrude a distance outside of thepercutaneous exposure 22 created through the outer skin S of thepatient. According to a preferred embodiment, at least the firstextender should have a “c-shape”, as seen along an axis transverse itslongitudinal axis, thereby defining a slot 63 that extends along itslongitudinal axis 50 and into the patient when attached to the screw.The slot should be sized to allow the targeting member to exit, so thatit is able to be delivered percutaneously, as shown in FIG. 1. Theinterior dimension 76 of the extenders should be such that they arecapable of receiving the appropriate driving tool (not shown) used toengage the screws and set screws. In addition, the interior dimension ofthe extenders should be able to accept a removable magnetic device 60for magnetically influencing the anchor members 14, as described furtherbelow.

Referring again to FIGS. 1-4, a targeting member is shown attached tobiocompatible device 44 by a tethering means 42. The targeting memberhas a first end 52 and a second end 54. The first end is designed topenetrate the tissue and is shaped to enlarge the opening while creatinga pathway through the tissues as the targeting member is advanced invivo. At least the first end of the targeting member is composed of asteering material capable of being magnetically influenced, as describedhereafter.

As shown in non-limiting embodiments of FIGS. 7a-e, the targeting member20 may be made from a flexible, semi-rigid, or rigid material, eachincludes the steering material 84 located on the first end. FIG. 7aillustrates an embodiment of a semi-rigid targeting member in the formof rod-like member with steering material 84 disposed on its first end52. The first portion 78 of the rod is made of a flexible materialcapable of safely colliding with bony or neural obstructions withoutcausing damage. FIG. 7b illustrates another flexible rod formed of aplurality of rigid consecutive segments 80 through which the tetheringmeans 42 extends to the first end (not shown). When the surgeon pullsthe tethering member at the second end taunt, the segments are forcedtogether and little movement is permitted between the segments. In theembodiment of FIG. 7c, the entire targeting member is composed of orcoated with a second biocompatible steering material 86. FIG. 7dillustrates another embodiment wherein the targeting member includes aball joint 88 attached to the tethering means. As with the embodiment ofFIG. 7b, the tension in the tethering member controls the amount ofpivot at the ball joint. Thus, when tension is released the rod comesflexible and the first end of the targeting member pivots on the ball.Alternatively, when the tension is reapplied to the tethering means, therod is solid again. This way the surgeon is able to safely guide thetargeting member around neural and bony obstructions as it moves throughthe body. Lastly, FIG. 7e depicts a rigid rod-like member formed from asolid biocompatible material 90.

The tethering means 42 may be made of any flexible or semi-flexiblebiocompatible material capable of allowing the device to navigate aroundneural and bony obstructions without damaging them. Examples of suitabletethering means may be in the form of a cable, cord or ligament.Moreover, the tethering means may be formed of a cannulated or solidmember. As discussed above, the first end 92 of the tethering means isattached to the second end 54 of the targeting member by any means ofattachment known in the art. Similarly, the second end 94 of thetethering means is attached to the biocompatible device 44 by any meansof removable connection known in the art. For example, the biocompatibledevice and tethering means could include corresponding threads that thesurgeon can rotate to disconnect the tethering means from thebiocompatible device.

According to a preferred embodiment, the biocompatible device is shownas an implantable interconnecting rod. The rod may be rigid, semi-rigidor flexible. Rigid rods are usually preferred for providing thenecessary stability during the healing process and arthrodesis, however,flexible rods have been found to provide for arthrodesis while allowingsome movement between bony structures that have been interconnected topreserve some motion. Moreover, like the tethering means thebiocompatible device may also be solid or cannulated.

Although the interconnecting rod is shown in FIGS. 1-4 asinterconnecting two pedicle screws, the surgeon could use anyappropriately sized rod having a length dimension capable ofinterconnecting three or more fastening means co-linearly implantedalong multiple vertebrae. It is also within in the purview of theinvention that any sized rod having various widths or diameters could beused so long as it is capable of stabilizing the bony structures forbony fusion. Although a rod-like member is exemplified herein, othersuch biocompatible devices known to one skilled in the art are alsocontemplated, for example, plates, clamps, etc.

FIG. 4 illustrates a hollow or cannulated flexible biocompatible devicein fluid communication with a cannulated tethering means. According tothis embodiment, once the rod has been properly inserted into thedesired location, the surgeon can use an insertion means 96 (syringe orthe like) to supply a biocompatible hardening material (e.g., cement,carbon, bone matrix) through the tethering means and into the interiorof the hollow rod. Although not required, the biocompatible device mightalso be made permeable and used to deliver constituents supplied by theinsertion means to the target area (e.g., bone growth/fusion material,medication, curing material, etc.)

As shown in FIGS. 1-4, each of the proximal ends of the extenders 12a-cprotrude outside of the patient's skin through percutaneous incisions 22so that the surgeon is able to insert instrumentation through theextender's interior portion to access the screw secured to the targetarea (vertebra). The extenders also enable the surgeon to insert themagnetic device or wand 60 into the selected extender to a positionproximate the corresponding anchor 14. The magnetic device includes aproximal 64 and a distal end 66. Magnetic material 62 is attached at thedistal end of the device and the proximal end may include a grip 100(not required) for the surgeon to hold the magnetic device. The wandshould be sized to extend the length of the extender.

The “magnetic material” 62 as used herein refers to either a permanentmagnet (as shown in FIG. 9) or an electromagnet (shown in FIGS. 1-4)which generates a magnetic field capable of influencing the steeringmaterial in the targeting member in vivo. As is known in the art, anelectromagnet is a magnet in which the magnetic field is produced by aflow of electrical current. One example of a suitable permanent magnetis a Neodymium Iron Boron (NdFeB) magnet since it is powerful and hasbeen approved by the U.S. Food and Drug Administration (FDA) forinternal use. Another example is the use of a recently developedbiocompatible non-metallic magnet, or plastic magnet, made from thepolymer PANiCNQ which is combination of emeraldine-base polyanailine(PANi) and tetracyanquinodimethane (TCNQ).

The “steering” material in the target member, as used herein, refers toany material capable of being influenced by the magnetic material 62.For example, the steering material may include any magneticallyattractive material or alloy, (e.g. steel, iron, etc). The steeringmaterial may be the same or different than that used for magneticmaterial 62 so long as it is capable of being influenced, e.g.,attracted or repelled. Moreover, either or both the magnetic materialand the steering material may be coated with any suitable biocompatibleelement, such as plastic. The type, shape, and size of the magneticmaterial and steering material should be suitable for internal use inpatients and provide the optimal magnetic field. Magnetic fields areused herein for navigating in vivo since these fields can penetratehuman tissue and bone without being distorted similar to x-rays, butwithout the danger of radiation and physiologic damage.

According to a preferred embodiment shown in FIGS. 1-4, the magneticmaterial employs an electromagnet having controls located in the handleor grip 100. At a minimum, the controls should include buttons andassociated circuitry that will allow the surgeon to turn theelectromagnet on 102 and off 104. Preferably, the controls also includebuttons and circuitry capable of increasing 106 or decreasing 108 thestrength of the magnetic field generated by the electromagnet and/orswitch between polarity (north and south poles). As is known, thepolarity of a magnet allows it to attract or repel magnetic materialwithin its magnetic field. The controls can also include a display 110used to indicate the strength of the magnetic field being applied.

The method of using the magnetic targeting system 10 of the presentinvention is described in accordance with the embodiment depicted inFIGS. 1-4. First, the anchoring member 14 (shown here as the multi-axialpedicle screw) is inserted into the desired target area (shown here asvertebra), as is known in the surgical art. The screw may be removablyattached to the distal end of the extender before or after attachment ofthe screw to the selected vertebrae. Once attached, the surgeon insertsthe targeting member into the proximal end of the extender whichprotrudes outside of the percutaneous exposure 22. The magnetic deviceis inserted into the next vertebra V2 which includes the anchoringmember (extender and screw), shown here as 12b. The magnetic material 62is disposed proximate the target area via wand 60. According to thisexample, the magnetic material is placed inside the connector portion ofthe screw, this may be done prior to, during, or after the targetingmember is inserted into the extender. If an electromagnet is used, thesurgeon will switch on the electrical current to begin generating anattractive magnetic field when in the proper position in vivo. If apermanent magnetic is used for the magnetic material 62, the surgeonsimply places it inside the connector portion of the screw, see FIG. 9.

As a result of the attractive magnetic field, the steering material inthe targeting member is pulled through the extender slot 63. Thestrength of the magnetic field generated by the magnetic material shouldbe capable of pulling the targeting member (including attached tetheringmean) toward the magnetic member such that the pointed first endpenetrates the tissue and creates a pathway through the tissues as thetargeting member is advanced toward the magnetic material. The use ofthe magnetic field to guide the targeting member, as compared toforcibly pushing the targeting member, as disclosed in the prior art,reduces the probability of damaging neural structures or breaking bonyobstructions encountered along its path.

Once the targeting member has reached the magnetic material 62positioned inside the connector portion of the screw, the surgeonremoves it from the anchoring member and places it into the nextanchoring member (extender and screw), shown here as 12c attached tovertebra V3. The aforementioned procedure is then repeated insideanchoring member 12c. If an electromagnet is used, the electricity alongthe magnetic member is turned on and the strength of the magnetic fieldgenerated pulls the targeting member through the passageway 30 of thescrew secured to V2 and toward the magnetic member located inside thescrew secured to V3, see FIG. 2. If a permanent magnet is used, thesurgeons simply places the distal end inside the connector portion ofthe anchor.

As described before, the pointed first end of the target memberpenetrates the tissue and creates a pathway through the tissues as itmoves toward the magnetic material. This technique of threading throughthe screw does not require the surgeon to try to align multiple pediclescrews along the fixed path of the rod. Moreover, the continuousmagnetic attraction of the targeting member toward the pedicle screwreduces the possibility that the target member will be diverted bystructures in the anatomical topography that may cause it to penetrateunintended areas. In addition, the present invention allows the surgeonto avoid a given anchor member. In such a circumstance the surgeon caninsert the magnetic material into that extender connected to the anchormember that is to be avoided. The magnetic material maybe either apermanent magnet or electromagnet having the same polarity as that ofthe targeting member. This will repel the steering material of thetarget member from that target area.

Once the final vertebra is reached, the magnetic member is used to pullthe targeting member through the slot in the upper opening 43 of thepedicle screw and along the interior length of the extender until itreaches the proximal end protruding out of the incision. The surgeon canthen grasp the targeting member and attached tethering means, see FIG.3. The tethering means located outside the patient is then used by thesurgeon to gently pull the attached biocompatible member (rod) along thepath formed through the tissue by the targeting member and through theconnector portion of the pedicle(s) until the biocompatible memberreaches the last vertebra, as shown in FIG. 4.

If the tethering means and interconnecting rod are hollow, the user candisconnect the targeting member and releasably attach an injection means96 thereto. The injecting means can be used into supply any suitable anyflowable, biocompatible material inside the rod. One example of asuitable biocompatible material includes at least one a hardeningmaterial that will cause the rod to become rigid.

Otherwise, the rod might be filled prior to the introduction of ahardening material. For example, the rod might contain ferroelectricmaterial that allows the rod to remain flexible during insertion processuntil exposed to an electric current. This is particularly suitable ifused in conjunction with the electromagnet embodiment previouslydescribed. Once the flexible rod is positioned at the final desiredlocation (secured to pedicle screws), the rod may then be exposed toelectric current in the electromagnet by inserting the magnetic meansinto the extenders. The electric current causes the ferroelectricmaterial to harden to make a substantially rigid rod. Thus, the contourof the rod corresponds to the natural curvature of the surroundinganatomy.

As discussed above, the connector portion of the screw is constructedand arranged to receive a set screw 32 therein. The set screw isinserted into each of the extenders and threadably attached by thedriving tool (not shown) positioned in the extender and inserted in toolopening in the screw. The interconnecting rod 44 is sandwiched betweenthe upper portion of the head and the set screw. This acts to secure therod onto the screws. The extenders are then removed from the connectorportion of the screw and the exposures closed.

Referring to an alternative embodiment shown in FIG. 8, the targetingsystem of the present invention does not require the use of an extensionmember for insertion of the targeting member in vivo. The anchoringmember may be implanted and the exposure closed with no external accessthereto. The proximal end of the implanted anchoring member may includeeither a permanent magnet or a remotely controlled electromagnet, as isknown in the art. Thus, the targeting member 20 may be directly insertedand fed into the body through an incision created by the surgeon. Aswith the previous embodiments, the magnetic portion of the anchoringmember is capable of attracting or repelling the targeting member placedinside the patient.

Any of the aforementioned embodiments of the system and techniques ofthe present invention can employ any type of known imaging system todetermine and locate placement of any of the aforementioned structuresin vivo. For example, insertion of the anchor member into the bonystructure can be pre-planned by CT scan, x-ray, or the imaging meansknown in the art.

The present system may also include a feedback system having at leastone detection element 120 (two are shown in FIG. 1) disposed outside andproximate the patient to determine the position of the targeting memberand/or biocompatible member in real-time. According to one, albeitnon-limiting embodiment, the detection element is an audio receiver orpickup capable of audibly detecting when the targeting member andmagnetic means connect or “click” together. This way, the surgeon canimagelessly determine that the targeting member has reached themagnetized portion of the anchoring member. This may be used inconjunction with a tactile sensation produced when the targeting memberand magnetic means connect. This tactile sensation of the two elementsmeeting will be felt by the person holding the tethering means.

Although the invention is described with reference to stabilization andfusion of adjacent spinal vertebrae, it is hereby contemplated thatdevices and methods disclosed herein could be used in all types ofjoints (ankle, interdigital, etc) found in the human or animal body.Although a rod-like member is exemplified herein, other suchbiocompatible devices known to one skilled in the art are alsocontemplated, for example, plates, clamps, etc.

All patents and publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

It is to be understood that while a certain form of the invention isillustrated, it is not to be limited to the specific form or arrangementherein described and shown. It will be apparent to those skilled in theart that various changes may be made without departing from the scope ofthe invention and the invention is not to be considered limited to whatis shown and described in the specification and any drawings/figuresincluded herein.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objectives and obtain theends and advantages mentioned, as well as those inherent therein. Theembodiments, methods, procedures and techniques described herein arepresently representative of the preferred embodiments, are intended tobe exemplary and are not intended as limitations on the scope. Changestherein and other uses will occur to those skilled in the art which areencompassed within the spirit of the invention and are defined by thescope of the appended claims. Although the invention has been describedin connection with specific preferred embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention which are obvious tothose skilled in the art are intended to be within the scope of thefollowing claims.

What is claimed is:
 1. A magnetic targeting system suitable forfacilitating navigation to a target area located in vivo, said systemcomprising: a targeting member having a first end and a second end, saidsecond end attached to a biocompatible device by a tether and at leastsaid first end includes a steering material influenced by a magneticfield, said first end is constructed and arranged to readily passthrough tissue and create a pathway for said targeting member to atarget area located in vivo; and at least two anchoring members, eachsaid anchoring member having a proximal end and a distal end, saiddistal end constructed and arranged to secure to said target arealocated in vivo, an extender coupled to each said anchoring member, saidextender having an open top and a aperture juxtaposed to a bottom end ofsaid extender, wherein said proximal end includes a magnetic materialthat influences the traversal of said steering material in vivo; saidtargeting member is of a size which enables said targeting member topass into first extender through said top of said first extender,through said first extender and out of said first extender through saidaperture of said first extender, said targeting member is also of a sizewhich enables said targeting member to pass into second extender throughsaid aperture, through said second extender and out of said secondextender through said open top, whereby, the magnetically influencedproximal end of said anchoring member interacts with said first end ofsaid targeting member guiding said targeting member through tissue suchthat said connected biocompatible device is positioned relative to saidtarget area.
 2. The magnetic targeting system of claim 1, wherein saidsystem includes a real-time feedback mechanism to verify location invivo of said biocompatible device.
 3. The magnetic targeting system ofclaim 2, wherein said real-time feedback mechanism includes tactilefeedback to verify location in vivo of said biocompatible device.
 4. Themagnetic targeting system of claim 1, wherein said magnetic material isan electromagnet.
 5. The magnetic targeting system of claim 1, whereinsaid magnetic material is a permanent magnet.
 6. The magnetic targetingsystem of claim 1, wherein said biocompatible device is an implant orsurgical instrument.
 7. The magnetic targeting system of claim 1 whereinsaid biocompatible device is formed from a material selected from thegroup consisting of rigid, semi-rigid, or flexible.
 8. The magnetictargeting system of claim 1, wherein each of said at least two anchormembers is a fastening means for attaching to a bony structure and saidbiocompatible device is an interconnecting means.
 9. The magnetictargeting system of claim 1, wherein said targeting member is formedfrom a rigid material.
 10. A magnetic targeting system for facilitatingnavigation of a biocompatible device to a target position connectinganchoring members secured in vivo, comprising: first and secondanchoring members, said first and second anchoring members each having adistal end configured to secure to a body structure located in vivo anda proximal end including a connector with a transverse passageconfigured to receive a portion of a biocompatible device, thebiocompatible device being lockable to the first and second anchoringmember connectors with locking members that engage the connectors, afirst extender having a proximal end and a distal end that is releasablycoupleable to the connector of the first anchoring member, and a secondextender having a proximal end and a distal end that is releasablycoupleable to the connector of said second anchoring member, each ofsaid first extender and said second extender having an interior passagethat extends along the length of the extender between a proximal endopening and a distal end opening, the interior passage sized to receivea locking members therethrough and a driver associated with the lockingmembers, each of the first extender and second extender also having anaperture in connection with the distal end opening and extendingtransversely through the interior passage, and a slot in connection withthe aperture and extending along the length of the extender; a targetingmember having a first end and a second end, said second end attached tothe biocompatible device by a tether, said first end including asteering material influenced by a magnetic field and configured toreadily pass through tissue and create a pathway along said targetposition, said targeting member sized to pass through the proximal endopening, the slot, and the aperture; and a magnetic device having aproximal end and a distal end, the distal end including a magneticmaterial that influences said steering material, the distal end beingpositional proximate the aperture of the second extender, the targetingmember is attracted to the distal end of the magnetic device to definesaid pathway along the target position, the connected biocompatibledevice being configured to follow the targeting device along the pathwayinto the target position connecting the first and second anchoringmembers.
 11. The magnetic targeting system of claim 10, furtherincluding a real-time feedback mechanism to verify the position of thebiocompatible device.
 12. The magnetic targeting system of claim 10,wherein said magnetic material is an electromagnet.
 13. The magnetictargeting system of claim 12, wherein the proximal end of the magneticdevice has a handle that includes controls for operating theelectromagnet.
 14. The magnetic targeting system of claim 13, whereinthe controls include a switch for turning on the electromagnet.
 15. Themagnetic targeting system of claim 14, wherein the controls can increaseand decrease the strength of the electromagnet.
 16. The magnetictargeting system of claim 10, wherein the magnetic material is apermanent magnet.
 17. The magnetic targeting system of claim 10, whereinthe targeting member is semi-rigid with a portion of the targetingmember proximate the first end being made of flexible material.
 18. Themagnetic targeting system of claim 10, wherein the targeting member isrigid.
 19. The magnetic targeting system of claim 10, wherein the firstand second anchoring members are pedicle screws and the biocompatibledevice is a rigid spinal rod.
 20. The magnetic targeting system of claim19, wherein the first and second pedicle screws are multi-axis pediclescrews.
 21. The magnetic targeting system of claim 20, including a thirdpedicle screw and a third extender releasably coupleable to a thirdconnector of the third pedicle screw, the third extender having aproximal end and distal end that is releasably coupleable to a connectorof the third pedicle screw, an interior passage that extends along thelength of the extender between a proximal end opening and a distal endopening, the interior passage sized to receive a locking membertherethrough and a driver associated with the locking member, the thirdextender also having an aperture in connection with the distal endopening and extending transversely through the interior passage, and aslot in connection with the aperture and extending along the length ofthe extender.